This invention relates to a support device for fitting a socket core on an end of a chill-mould for centrifugally casting iron pipes.
Such a core support or "head" is described in U.S. Pat. No. 3,612,162 and French Pat. No. 2,053,388, and is mounted on the end of an articulated arm so as to be retractable away from the front of a centrifugal chill-mould and out of the path of the cast pipe when it is axially extracted from the mould. The head includes a metal seat that acts as a direct chaplet for the sintered sand socket core, and articulated dogs for gripping the core on the inside to insert it into a recess in the end of the mould. The head contains a jack for actuating the dogs between a core gripping position and a retracted position.
This technique of radial interior dogs directly contacting the interior of the sand core requires the repeated radial adjustment of the dogs to prevent them from becoming too solidly inserted in the sand core's interior, and the periodic readjustment of the dogs' position according to the diameter of the annular core's interior cavity, which has wide dimensional tolerances due to the wear of the core mould box resulting from abrasion by the sand.
Furthermore, the articulated levers on the dogs are actuated by a jack to engage the dogs in the sand core's interior. The jack's stroke must be carefully controlled to prevent the dogs from entering the core's interior too deeply, creating the risk of breaking the relatively fragile sand core.
Finally, due to the risk of the dogs going too far into the sand cavity, and the ensuing commencement of a rupture of the core, the use of a dog core support such as described in the two patents above is limited to relatively light weight socket cores; for example, those for pipes with an interior diameter of 150 mm.